Effect of Blue Light on Coaggregation Between Fusobacterium nucleatum and Streptococcus sanguinis

Coaggregation by bridging bacteria such as Fusobacterium nucleatum is considered a key element in dental biofilm development and maturation. Previous studies showed that sublethal exposure to blue light caused damage to cell membrane integrity. The aim of the present study was to test the effect of blue light phototoxicity on this bacterium’s ability to coaggregate with the early colonizer Streptococcus sanguinis. Fusobacterium nucleatum bacterial cells were suspended in coaggregation buffer (CAB) and exposed to blue light (400–500 nm) for 0, 70, 140 and 280 s (i.e., fluences of 0, 96, 192 and 384 J/cm2, respectively). Following blue light exposure, samples were mixed with Streptococcus sanguinis suspensions and coaggregation was measured using a visual scale, spectrophotometric analysis and light microscopy. Results showed that blue light exposure significantly reduced the ability of Fusobacterium nucleatum to coaggregate with Streptococcus sanguinis. These results suggest that blue light antibacterial phototoxicity may be considered as a viable option in preventing dental biofilm-related conditions.